Preparation of in situ grown silicon carbide whiskers onto graphite for application in Al2O3-C refractories

Abstract

C-SiC composite powders were prepared by salt-assisted synthesis from Si powders, graphite, and a molten salt medium (NaCl and NaF) with the molar ratio of Si/C = 1/2 at 1300 °C for 3 h. After the C-SiC composite powders part and complete replacement of the graphite, the mechanical properties, oxidation resistance and slag-corrosion resistance of the Al2O3-C materials were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), as well as with dedicated equipment. The results indicated that SiC whiskers, with lengths of 10–50 nm, formed on the surface of the flake graphite, and the activation energy of oxidation of the C-SiC composite powder increased by 45.72 kJ mol−1 as compared to that of flake graphite. Furthermore, the decarburization area and slag erosion area of the Al2O3-C material decreased after 3 wt% of C-SiC composite powder was substituted for the flake graphite. Meanwhile, the cold modulus of rupture was maintained when 3 wt% of C-SiC composite powder was added. This improved both the oxidation and slag resistance of the Al2O3-C materials.